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Star‐Like Poly( N ‐isopropylacrylamide) and Poly(ethylene glycol) Copolymers Self‐Arranged in Newfound Single Crystals and Associated Novel Class of Polymer Brush Regimes with V‐Type Tethers
Author(s) -
Mahmoudi Mojgan,
Agbolaghi Samira,
Mozaffari Zahra,
Abbaspoor Saleheh,
Massoumi Bakhshali,
Sarvari Raana,
Hosseinzadeh Nasrin
Publication year - 2018
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201700638
Subject(s) - polymer chemistry , ethylene glycol , copolymer , materials science , peg ratio , atom transfer radical polymerization , poly(n isopropylacrylamide) , polymer , small angle x ray scattering , chemistry , scattering , organic chemistry , composite material , physics , optics , finance , economics
Linear poly(ethylene glycol) (PEG)‐ block ‐poly( N ‐isopropylacrylamide) (PNIPAM) and star‐like three‐arm PEG‐ star ‐(PNIPAM) 2 copolymers having one PEG and two PNIPAM blocks are synthesized by atom transfer radical polymerization (ATRP). Single crystals of these block copolymers are grown from amyl acetate and toluene dilute solutions. To recognize PNIPAM and PEG thicknesses, small angle X‐ray scattering (SAXS) is applied. V‐type brushes behave differently from linear brushes because doubly grafted PNIPAM blocks from a common point onto PEG substrate exert a higher osmotic pressure, leading to a thinner crystal. In addition to three ordinary regimes, a fourth or extremely stretched regime is detected for V‐type PNIPAM brushes. Although in PEG 5000 ‐ star ‐(PNIPAM) 2 single crystals with overall PNIPAM molecular weight of 37 000 g/mol, each PNIPAM arm is shorter than PNIPAM grafts in linear PEG 5000 ‐ block ‐PNIPAM 26000 single crystals, their switching point from second to third regime is significantly lower (22 vs 33 °C). The V‐type configuration of PNIPAM brushes cause them to be entered into the extremely stretched or fourth regime, which has not been previously detected for coily brushes. The boundary between third and fourth regimes for PEG 5000 ‐ star ‐(PNIPAM) 2 single crystals is verified at 31.5 and 23.5 °C in amyl acetate and toluene, respectively.